Abstract
Using combined gas chromatography-mass spectrometry, the mass spectrometric fragmentations of 20 kinds of methyl sterol and their corresponding 10 kinds of sterol which are related to cholesterol families have been investigated.
The patterns of the spectra of 4-metyl sterols were generally similar to those of the corresponding sterols except for following ion j (Table-1). Characterstic ion j was observed at m/e [M- (H2O+29)] + for 4-monomethyl sterols and at m/e [M- (H2O+43)] + for 4, 4-dimethyl sterols, demonstrating that this ion serves to distinguish 4-methyl sterols from all other groups of sterol. It has been suggested that the formation of this ion probably involves loss of C-4 methyl group together with C-3 functional group from molecular ion.
Characteristic fragmentations of saturated sterols, and of monounsaturated (Δ5, Δ7, Δ8 (14) , Δ14), diunsaturated (Δ5, 7, Δ7, 9 (11) , Δ8, 14, Δ7, 14) and triunsaturated (Δ5, 7, 9 (11) ) sterols were also described.
